Heretofore, as this kind of the cable sealing end, (1) the thing which fixes an epoxy unit in the inside of a base of a porcelain bushing and installs a molded rubber stress-relief cone to the aforementioned epoxy unit (for example, refer to Patent document No. 1), or (2) the thing which controls the electric field by the molded rubber stress-relief cone itself without providing the above-mentioned epoxy unit (for example, refer to Patent document No. 2) are known.
However, in the cable sealing end of (1), although the decision of the position of the molded rubber stress-relief cone can be performed easily, because the predefined interfacial pressure must be given to the interface between the molded rubber stress-relief cone and the epoxy unit, there is a difficult point which must arrange the pressure device having such as the relatively-large spring unit in the neighborhood of the molded rubber stress-relief cone. And, in the cable sealing end of (2), although it is not necessary to arrange the above-mentioned pressure device, because it is necessary to seal the insulating oil in the inside of the porcelain bushing by the metal fitting or the tape which are used only for oil-stopping, the reliability of the sealing part (oil-stopping part) is apprehended as shown in next.
First, the structure of the sealing part (oil-stopping part) such as the tape by the construction at the site has the influence on the airtightness by skill of the worker.
Second, because it is necessary to provide the component such as the metal fitting which are used only for oil-stopping, and because the operation of winding of the sealing tape is necessary, the structure becomes complex and also the workability deteriorates.
Third, when the insulating oil which is filled in the inside of the porcelain bushing contacts to a semi-conducting body part of the molded rubber stress-relief cone, there is a possibility that the physical property of the semi-conducting body part is influenced.    Patent document No. 1: Patent publication number H04-193018    Patent document No. 2: Patent publication number 2007-159271